Wanted: feedback from drivers late model 300-340 Cummins

[Ductape]

The short version: if you have a recent Cummins 300-340 hp range does your coach hold 6th gear crossing interstate overpasses and mild grades? Or does it downshift at any mild rise?

Thanks for your feedback, and if you want to read all the whys and wherefores, the next post I'll drone on. :B

[msturtz]

What is being missed here are a few things. When we had a towable we were about 60' long & 8'6" wide with a bumper pull overall length. I drove around downtown Salt Lake City UT & Portland OR including parallel parking. It wasn't fun but I was able to do it without trading paint with anyone. In certain situations other rude drivers were laying on their horn as if that would speed me up. I have also taken our DP off road onto a one lane gravel service road. Again slow speed is key don't be afraid of getting out and looking "GOAL". Many parks won't take longer rigs due to inexperienced drivers rather than actually being unable to accommodate them. Modern rigs have a 55 degree wheel cut. That makes them much easier to turn.

[Mile_High]

We have the longest Winnie made in 2013 at 43'6" and in the year and half we have had it, I've struggled fitting a few times, even at KOAs. Sometimes its the tight turns that get me, not the length of the driveway. We stayed at a private campground in Truckee, CA and I thought I would never get that thing parked in there.

[DSDP_Don]

Just to clarify what "tropical36" brought up, there really isn't anything around San Francisco, even for a small rig that is worth staying in. There is a parking lot near the stadium, but it is literally that, a parking lot.

The Petaluma KOA is actually one of the really good spots to see San Francisco either in a Class B or a 45' DP.

[tropical36]

Ductape wrote:
But that's exactly the point. You ended up in KOA... Thanks but no thanks. 🙂

I said once and not the norm, with however you one might feel about a particular stay. The thing is, we're not about to go without what we like in a coach, just because it might be a little large for some RV parks and again, far and few in between.
You should see the size of some rigs, inside Glacier NP at their Apgar campground, for instance.

[Ductape]

But that's exactly the point. You ended up in KOA... Thanks but no thanks. 🙂

[tropical36]

A little off topic, but it seems that the only people that claim not being able to find large enough sites in parks are the ones that have never owned a large one of 40ft or more. Occasionally yes, but not the norm.
I do remember once with being on the phone and calling around in the San Francisco area and not having much luck. It was summer and of course most of the CA coast line was pretty active with RV's. Anyway, we went on up to the Petaluma KOA, where you could have brought in a semi without much difficulty. They even had a field for overflow, in case they didn't have a site available upon your arrival. Their van conducted tours of the city, right from the office, so not a problem with being up the road a ways and we used our toad for getting to the ferry, as well. Just saying, that there's always someplace to park, no matter what your size.

[msturtz]

gutfelt wrote:

msturtz wrote:
I'm running a 2014 Thor Palazzo 33.3. It has a ISB 300 and Allison 2100 MH. I could go to ISB 340 / 700 with the same transmission. I have towed a 2015 Suburban, 2015 GMC Acadia Denali, 2016 Yukon Denali XL, and 2017 Ford Explorer. The I am at my max GCWR when I tow the Yukon and the motor home is empty. The transmission does downshift. I have traveled over the rocky mountains 4 times with this setup (pulling the Acadia) we had no problems. I probably will upgrade to ISB 340.

A suburban weighs more than a 2015 yucon or explorer

I have a Yukon XL it weighs more than a Suburban.

[DSDP_Don]

"Ductape".....Here are some talking points, or should I say pictures. The first is my 37'Diplomat at the Watchmen Campground inside Zion. You can see there is room for another six feet.



We don't take photos of the coach in the campsite like we use to, so I really don't have that many pictures of the coach itself. In this photo, we're at Yosemite Upper Pines at Thanksgiving. The coach in the background is a 41' Monaco Camelot. My 40' is to the right of the turkey. There are several sites there that will take a 40' coach.



Lastly...I only have the view through the windshield as we enter the Yellowstone west gate.:B We stayed at Fishing Bridge.



The new coaches have a 55+ wheel cut and can really crank around to get into tight spots. Just some confusion for your decision!

[Ductape]

Thanks, Don. If I could talk both of us into a forty footer I'll skip the Ventana and go directly to the Dutch Star. :B

[DSDP_Don]

"Ductape"......We owned a 36' 2005 Monaco Diplomat for almost ten years and took it all over the country, including MANY national parks, where we camped inside the park. Those included Yellowstone, Yosemite, Zion, Rocky Mountain etc. We eventually sold that coach and bought a TRUE 40' coach, our Newmar Dutch Star. We've taken that coach to all the same places we took the Diplomat. The Dutch Star is 36" longer than the Diplomat that measured 37'.

In all honesty, sites typically larger than 35' are fewer and far between, but they do exist and we just have to plan ahead at places like Yellowstone.

With all that said, put away your engineering degree and angst, and buy a 40' Ventana with the 400 ISL. All your problems will be solved.

In 4 years of owning the Dutch Star, we haven't regretted adding the 36" in length.

[tropical36]

Ductape wrote:
Backstory- we're in the market for a short coach, less than 36 feet. It's our preference (due to the types of parks we enjoy). Likely a Newmar Ventana or Ventana LE or Tiffen RED. We'll pull a large toad. Perhaps new, but we'll also consider going back a few years, but not before DEF engines.

I dislike a powertrain that's maxed out on torque and has to shift gears too often. Defeats the whole purpose of a diesel so to speak. And I've operated some trucks like that.

The real technical stuff: Most coaches in this range are built with the Allison 2000 series trans, a few have the 3000 Allison. The smaller transmission has limited torque handling capability and is used with the ISB 300 or 340, with peak torque ratings of 600 to 700. The Allison 3000 enables use of the ISB 360 which is 800 lb-ft torque. Which seems like not much difference, right?

But here's the thing; the 2000 series requires the use of torque managed engines, which limit the torque when shifting (not a bad thing) and also the torque in certain gears (and this is my concern). The 2000 series trans allows up to 700 lb-ft in gears 3-5. In other conditions it's limited to 575 lb-ft. Limitations on the Allison 3000 are not a concern with the ISB, as the trans can handle 1250 lb-ft and torque management is not required.

So... it would appear that the ISB360/Allison 3000 combo can draw on all 800 lb-ft of torque to maintain speed on a grade in any gear, whereas the ISB340/Allison 2500 by comparison can only use 575 lb-ft in 6th gear. That sounds like a recipe for easily dropping out of 6th with the smaller transmission. But does the real world experience match?

Thanks for your patience in reading my dissertation, and I appreciate your feedback.

Rule of the thumb, without all the technicalities, is to have around 10HP per foot, which provides a decent amount of torque and is usually more than sufficient to handle a fairly heavy toad as well. It ends up being with the amount of weight you're trying to move, per the engine size.
You stated under 36ft, so story short, I'm most sure if you get a 340HP power plant in a 34ft coach, you're good to go as well or better than many. Anything close, should serve you well, also.
With our almost 41ft and grossing a little less than 37K lbs. including the toad, we spend most of our time in 6th gear, over all kinds of terrain.

[Ductape]

I made an opportunity to test two coaches with the varying power trains, and I'll share the result in case this interests someone else shopping in the future. Coaches were identical models, but differing trim level; one with 340/2500 powertrain and the other with 360/3000. Same gear ratio in the axle and similar weights, the higher optioned coach with the 360 probably about a thousand pounds heavier due to options.

The 360 powered coach was noticeably more responsive at low speeds and accelerated more quickly from a dead stop. As expected due to torque limiting in lower gears with the Allison 2500. This was a difference you could feel in the seat of your pants.

The 2500 does indeed shift more smoothly than the 3000. Shifts from the bigger transmission were smooth, but perceptible. The 2500 shifts so smoothly (again with torque management) that they were imperceptible.

On a grade -using a short hill that's about 4% at it's worst slope as a benchmark- I ran the hill at 65 with each coach in economy mode, cruise control on. The 340/2500 lost 2 mph on the hill and regained speed after cresting the hill, no gear changes of course. The 360/3000 coach lost 1 mph and then accelerated back up to 65 on the climb, all in 6th gear. Speeds measured with a GPS.

Repeating the hill in normal mode and driving with my foot the less powerful coach dropped into 5th to hold speed.

In the intermediate gears 3-5 (where the Allison 2500 is not torque limited), the difference in these coaches is not really perceptible. Accelerating or holding speeds on a grade in those gears the coaches feel very similar and the performance difference between 340 hp and 360 will not be felt. In gears 1,2 and 6 the effect of having the full 800 lb-ft of torque is perceptible.

[chuckftboy]

I have a 340 / 2500 combination and it never down shifts on overpasses or slight inclines It will down shift 6 to 5 in the hills but one would need to see it on the shift pad to know it happened.
As for increasing HP and torque, any Oasis shop can do it for about $450.00, its a simple program download. My son had his done last summer on his 2014 Excursion. Went from 300 hp 650 torque to 325 hp and 750 torque.

[Ductape]

How to uprate your Cummins

I expect there are aftermarket vendors too. Banks etc.